Text messaging is a widely applied communication mechanism and the installed base of related network elements is significant. The present systems can provide value-added services to senders of short messages, but so far practical solutions for providing value added services to the receiving party have not been available.
The basic short message architecture relies on two main primitive services, mobile originated short message service (SM MO) and mobile terminated short message service (SM MT). In SM MO the short message is delivered from a sending mobile station to a service centre assigned to the sending mobile station, and is stored therein. In SM MT the service centre of the sending mobile station is delivered the stored short message to the receiving mobile station.
In conventional solutions, short messages are routed directly from the service centre to the destination, without necessarily involving any of the home network elements of the receiving mobile station. It is clear, however, that for any applicable mobile terminated value added services, information for provision of the services has to be maintained in the home network of that mobile station.
3GPP (3rd Generation Partnership Program) standardization work-groups have been actively working on an improved architecture that would allow provision of value added services also to the receiving users. The proposed solutions disclose a new network element and two models to how to apply it. The new network element is a mobile terminated short message router (MT SMS router) that is implemented in the home network of the receiving user. MT SMS router is involved in the transmission of short messages by diverting the conventional query for routing information from the home location register of the home network to the MT SMS router, and returning as the routing information the address of the MT SMS router, instead of the location of the receiving mobile station. In consequence, the subsequent short messages are first delivered to the MT SMS router where actions of value added services may be performed before the short message is relayed to the actual destination mobile station.
In a transparent mode the mobile terminated traffic is re-directed through the MT SMS router but the control of transmissions and retransmissions remains in the originating end. If the receiving mobile station cannot be reached, the negative acknowledgement is forwarded to the MT SMS router, but then immediately relayed to the SMS service centre of the sending mobile station. In a conventional manner, the SMS service centre of the sending mobile station will then attempt to send the message according to an applied retransmission scheme. This transparent mode is typically strongly preferred, because it can be implemented without substantial changes to the operations in the sending mobile station end. The disadvantage is, however, that the control of retransmissions is in one location and the control of value added services in another. This may cause mismatch in the operations of some value added services, and thus prevent or at least impede successful implementation of MT value added services.
For example, one of the possible value added services for a receiving user is provision of carbon copy messages. In the auspices of the service, a copy of some or all received short messages is generated and delivered to a predefined other receiving mobile station. In case the original receiving mobile station is not reached with the first delivery attempt, the SMS service centre of the sending mobile station will retransmit the short message according to a predefined retransmission scheme. It may, however, be that the other receiving mobile is able to receive the carbon copy message already with the first attempt, or with any attempt before the original receiving mobile station is reached. In this case the delivery of carbon copies will continue until, for example, the timer is exceeded or also the original receiving mobile station is reached. This is not acceptable, because ease of use and reliable operation are of great importance, and this is especially true with widely used services, like SMS.
A non-transparent mode intercepts the mobile terminated SMS in the same way as the transparent mode, but the control of transmissions and retransmissions is in this case transferred to the MT SMS router. The MT SMS router stores short messages forwarded to it locally and returns automatically a positive acknowledgement to the sending SMS service centre. In case the delivery of the short message fails, it is the MT SMS router that retransmits the short message according to the applied retransmission scheme. The advantage of the non-transparent mode is that the control of value added services and the retransmissions are in the same place, and any possible mismatch between them can thus be easily eliminated. The problem is, however, that the transfer of control necessitates provision of a false indication to the sending party. On the basis of such indication, the sender may assume that his message is received, even if the receiving party may be out of reach for quite some time. This causes unacceptable confusion for the users of the value added service.